A UN human rights official has been roundly condemned for suggesting that the US government may have orchestrated the September 11 terrorist attacks.

Richard Falk, a retired professor from Princeton University, wrote on his blog that there had been an "apparent cover up" by American authorities.

He added that most media were "unwilling to acknowledge the well-evidenced doubts about the official version of the events" on 9/11, despite it containing "gaps and contradictions".

And he described David Ray Griffin, a conspiracy theorist highly regarded in the so-called "9/11 truth" movement, as a "scholar of high integrity" whose book on the subject was "authoritative".

Ban Ki-Moon, the UN Secretary-General, described the comments as "preposterous" and "an affront to the memory of the more than 3,000 people who died in the attack." But Mr Ban said that it was not for him to decide whether Prof Falk, who serves the organisation as a special investigator into human rights abuses in the Palestinian territories, should be fired by the UN.

Vijay Nambiar, Mr Ban's chief of staff, said this was up to the human rights council, a 47-nation body based in Geneva, Switzerland, that was created by the UN in 2006.